The Parallels Desktop 4 for Windows and Linux edition comes hot on the heels of a special bundle of its Parallels Desktop 4.0 for Mac hypervisor aimed at helping customers make the switch from Windows PCs to Macs. And it's similar to the Parallels Workstation Extreme edition announced in April that was tuned specifically for Hewlett-Packard's "Gunnison" Z800 workstation, which uses Intel's quad-core Xeon 5500 processors and supports the nVidia Quadro FX 3800, 4800, and 5800 graphics cards running at near-native speeds even in a virtual environment.

All three desktop hypervisors are based on the same code base that was originally created for Intel-based Mac machines. That base Parallels hypervisor is a type 2 hypervisor, which means that the hypervisor runs atop of an operating system (Mac OS, Windows, or Linux) that then supports multiple virtual machines. This type 2 hypervisor is distinct from the type 1, or bare-metal, hypervisor that El Reg told you Parallels was working on back in March for servers and, presumably, for desktops.

In the meantime, Parallels wants to squeeze as much dough as it can out of the Desktop 4 code base, which has been given the name FastLane after some performance tweaks allowed the hypervisor to run "up to eight times faster than ever before." If that is the case, then the prior versions must have been truly awful in terms of performance, and it might not be something Parallels wants to mention.

Anyway, the FastLane hypervisor makes use of Intel's VT and Advanced Micro Devices' AMD-V virtualization-assisting electronics (which is another way of saying that it requires it, so watch out for older x86 and x64 desktops). And it can run atop Windows or Linux hosts, either 32-bit or 64-bit versions. (Obviously, if you want to run a 64-bit operating system in a VM, you need to have a 64-bit host. 32-bit VMs work on either 32-bit or 64-bit hosts).

The FastLane hypervisor within the Windows and Linux variant of Desktop 4 can span as many as eight processor cores - as much as a Xeon 5500 workstation requires, but short of the twelve cores an "Istanbul" Opteron 2400 workstation can have - and it can allocate 8 GB of main memory to each VM. Each VM can have 2 TB of virtual disk space and up to 16 virtual Ethernet adapters.

In addition to the hypervisor, Desktop 4 for Windows and Linux includes a feature called Transporter, which converts a PC image running on a physical machine or a PC image in another VM format to the Parallels Desktop format. The package also includes a feature called Compressor, which defragments and compresses the files relating to VMs on the PC to cut down on storage requirements, and Image Tool, a virtual disk formatting and sizing tool that can expand, split, and merge virtual drives. The Desktop 4 tool also has a templating feature that allows desktop administrators to pre-configure VMs with software so they can be propagated across the company and a directory of online virtual appliances that Parallels has packaged up.

Parallels is hoping that future Windows 7 customers are so frustrated by the Windows XP mode Microsoft is putting into Windows 7 that they decide to run Windows 7 as a host and Windows XP in a VM proper rather than the cut-down hypervisor Microsoft is using as an emulation environment for XP applications.

Parallels is offering an upgrade from its prior Parallels Workstation 2.2 versions for Windows and Linux, although it is not clear at press time what the upgrade price is. Desktop 4 for Windows and Linux is available today, and it costs $80 a pop in the United States and £55 in the United Kingdom. The hypervisor is only available in English, by the way. ®